107 
for ascertaining the velocity of sound. 
interval is 25", 632, and the mean of the whole 25", 869, 
making the difference just mentioned. 
Now 25", 869 + 0", 237=26", 106, which would have been 
the mean number of seconds had the observations with the 
Mount gun been continued during the same interval only as 
the experiments with the Fort gun. Then 26", 106 : o'', 237 : : 
12", 306 (the mean of the Fort observations) : o // ,ii2. Now 
12", 306 — 0 ,/ ,ii2=i2 // ,i94, which would have been the gene- 
ral mean of the experiments with the Fort gun, had the same 
been continued as long as the experiments with the Mount 
gun. Then the distance 13932,3 feet, divided by 12,194, 
will give 1142,5 for the motion of sound by the experiments 
with the Fort gun thus brought on ; and this also agrees, 
within a fraction of a foot, with the velocity according to Sir 
Isaac Newton ; and with the results by the two other cele- 
brated philosophers before named. Feet 
We then have by the Mount gun 1142,18 for the velocity. 
And by the Fort gun - - - 1142, 5. 
The mean is 1142,34, or very nearly the velocity above 
alluded to. Nothing could be more satisfactory than this 
general result ;* and it may be presumed, that the other re- 
sults in different states of the atmosphere are equally to be 
depended upon. 
The velocity also by the Fort gun, which, it will be recol- 
lected, is little more than half the distance of the Mount gun 
from the station, shows that sound travels equally during its 
progress. 
In the N E. monsoon, the sound was very indistinct at 
times ; this however does not appear to have sensibly affected 
* The results by the Mount gun may however be taken as the standard. 
